A guide to music files

By Mike Atherton 13 May 2018

Unless you listen to all your music on vinyl or tape, you’re probably using digital files and there are loads of different types. In this article, we’ll take a look at six of the most common file types and how they differ from each other.

Some file types like MP3 or AAC compress the file to make it smaller and more manageable, and with audio, this means sacrificing some quality. Some file types are ‘lossless’ which means they maintain the highest possible sound quality - but that does mean bigger files.

Contents

When we talk about audio files, it’s useful to understand what ‘bitrates’ are, particularly when it comes to streaming music. Bitrates simply describe how much data is being transferred in a given time frame, so a bitrate of 128 kbps means that 128,000 bits of data are being transferred every second. To put this into context, an uncompressed audio CD plays at 1,411 kbps, wheres the highest quality MP3 can only manage 320 kbps.

So let's take a look at six of the most popular types of audio file, and the pros and cons for each.

MP3

MP3 (or MPEG) is the file type that we’re most familiar with, it was developed in the 80s, and is still one of the most commonly used file types. Because it was created at a time when storage space was limited, MP3s compress the file to help save disk space. The downside to this is that some audio quality is lost.

MP3 files remove any sound data that you wouldn’t normally be able to hear but they also reduce the quality of other sounds which lowers the overall fidelity slightly. MP3 will never be able to deliver music exactly as it was recorded - but it’s still a good all rounder when it comes to maintaining good quality audio while reducing file size.

The great thing about MP3 is its reliability - just about every digital device that plays sound can play MP3 files.

AAC

AAC stands for Advanced Audio Coding and it was developed in the mid 90s in the hope that it would replace MP3, but despite being superior in many ways, AAC never quite overtook MP3.

A direct comparison to MP3 shows that AAC gives you smaller files and slightly better sound quality when played at the same bitrate, making it more efficient. Even though we haven’t adopted AAC as a way of managing all of our offline music, it’s more advanced compression means it’s great for online content. It’s the preferred file type for iTunes, and it’s also what YouTube uses.

AAC isn’t quite as universal as MP3 but it can be played on most smartphones and tablets these days, like iPhones, iPads, and Android devices.

Ogg Vorbis

This one can be a bit confusing - it’s different to most audio files because it works as a container for different file types. So an Ogg file can contain compressed MP3 data, or a high fidelity, lossless FLAC file (we’ll look FLAC files a little later).

The ‘Vorbis’ part is the compressed file type most commonly used with Ogg, and Ogg is the ‘container’ it sits in.

The benefit for companies that use this format is that it’s completely open source, meaning they don’t need to pay a licence fee to use it.

Ogg is the file format that Spotify uses, and when you compare it to MP3, it delivers comparable audio quality at around a 30% smaller file size - this means it’s great for streaming music.

There aren’t many devices that can play Ogg files natively, but for services like Spotify, that doesn’t matter because you never see the file itself - that’s all handled through your Spotify app.

WMA

Windows Media Audio was developed by Microsoft in the 90s, and like AAC, the intention was that it would largely replace MP3. But the main drawback with WMA files is that they only work if you have a Windows device. It’s possible to play them on non-Windows kit but you’ll need to use special software, or convert them to a different file type altogether.

In terms of sound WMA files do offer better quality to MP3 at higher bitrates, but at lower bitrates, they’re pretty much the same. So unless all you only use Microsoft devices, you’re probably best sticking to the ever faithful MP3.

FLAC

FLAC offers completely ‘lossless’ compression of audio data, meaning you get to hear your music at CD quality, exactly as it was recorded - it can also compress the file size by up to 60%. It’s been around since 2001 but has recently started to gain popularity thanks to streaming sites like Tidal, and Deezer adopting it as a way to stream 'Hi-Res' music.

Even though files are compressed, they’re still much bigger than MP3 files with the average 4 minute song coming it at around 30mb, compared to the highest quality (320kbps) MP3 at around 10mb. So if you’re thinking about joining a music streaming service that offers FLAC, just bear in mind that unless you’re always using Wi-Fi, you’ll need a good mobile data plan to avoid any nasty bills.

You shouldn’t have any trouble playing FLAC files - it’s supported by most devices including Android phones or tablets, and iPhones or iPads running iOS 11 or later.

ALAC

In short, ALAC is Apple’s version of lossless audio compression and in terms of audio quality, there’s no real difference between FLAC and ALAC - they both offer completely lossless CD quality audio. While it is proprietary, in 2011 Apple made ALAC open source, meaning it can be used and developed by anyone without having to pay a licence fee.

It’s unlikely that ALAC will ever overtake FLAC for lossless audio, because it doesn’t do anything different, and FLAC is still a little bit better when it comes to compressing files.

The main reason to choose ALAC over FLAC is if you’re already invested in iTunes and iOS because iTunes still doesn’t support FLAC, despite it being more widely accepted elsewhere.

Hopefully, that's helped you to understand what different music files do and why some are better than others - depending on what you're looking for.